Absorber to absorb acoustic sound waves and method for its production

ABSTRACT

In a so-called “hollow chamber absorber” comprising chamber-shaped intermediate cavities ( 7 ) between a supporting body ( 1 ), spacers ( 2 ) and a covering layer ( 5 ) acting as a covering unit ( 11 ), simultaneous deformation and connection of the covering layer ( 5 ) with the edge ( 4 ) of the supporting body ( 1 ) and the open front ends ( 3 ) of the spacers ( 2 ) of the preformed basic constructional unit ( 10 ) occur by using a stamp ( 8 ) whose front face ( 9 ) is configured according to the final state of the covering unit ( 11 ) on the basic constructional unit ( 10 ).

BRIEF STATEMENT OF THE INVENTION

The invention relates to an absorber for absorbing acoustic sound wavesand a method for its production.

BACKGROUND OF THE INVENTION

Such absorbers have already been known (DE 36 15 360 C2, WO 96/08812,DE-OS 27 24 172, DE 33 13 001 A1). Therein, honeycomb-like chambers inthe basic constructional unit, which consists of a supporting body andspacers and is produced via injection-moulding or an RIM-process, arecovered in the direction of the sound source by a covering layer. Thecovering layer comprises burl-like air chambers so that there occursfrictional damping when the “air cushions” vibrate and hit the edges ofthe spacers or it is smoothly tentered over a porous basic unitconsisting of foamed plastic, in particular, and is welded therewith atcertain locations.

It is the object underlying the invention to simplify an absorber ofthis type as regards its production and to improve it as regards itsfunction. Furthermore, its disposability shall, if possible, be improvedin that reusable material parts are used, in particular.

The invention is characterised in claim 1 as regards the absorber and inclaim 8 as regards the production method. Further improvements areclaimed in the subclaims.

The absorber is produced from two respectively integral units. Thespacers and the supporting body constitute a preformed basicconstructional unit which consists more particularly of deep-drawn ortransfer-moulded thermoplastic like polypropylene (PP), pressedthermoplastic or thermosetting plastic, injection-moulded thermoplasticor thermosetting plastic, relief-pressed or, respectively,relief-injected plastics, namely with fibre reinforcements, inparticular. These materials may be produced both from new and recycledproducts.

The following deformation processes may be used for producing the basicconstructional unit, in particular:

1. Low Pressure Technology (LPT), wherein plastic is pressed into therespective mould at low pressure between about 10 and 100 bar. Longglass fibers (LFG) having a fiber length of about 12 mm may also beused. In heating duct technology, PP (polypropylene) in particular ismixed with 20% of talcum.

2. Reaction Injection Moulding (RIM), wherein PU (polyurethane) ispreferably used as the plastic. In the case of fiber reinforcements(R-RIM) glass fibers are used in order to promote thermal stability.Transfer moulding is carried out at a low pressure of up to about 15bar.

3. Resin Transfer Moulding (RTM), wherein plastic, more particularlyepoxy, phenolic, vinyl resins, optionally reinforced with glass fibers,are pressed into the closed mould, preferably at a low pressure of up toabout 20 bar.

4. Injection Moulding, wherein high pressure between about 350 and 700bar is used for filling the polymer plastic into the casting mould.Reinforcements may equally be used.

5. Glass-mat reinforced thermoplastic method (GMT or AZDEL), wherein PP,for instance, is press-moulded with a glassfiber mat at pressuresbetween about 150 and 200 bar.

For relief-pressed plastic, the plastic is press-moulded with a textilestructure or a film between press moulds via LPT or GMT whereas, forrelief-injected plastic, the plastic is injected onto the textilestructure or the film in an injection mould.

On the other hand, the thin covering unit is a particularly thincovering layer which is pressed directly onto the basic constructionalunit from a straight plane and deformed in the process, but which isable to vibrate in certain regions at least. The vibrant regions shouldrespectively be situated between those locations of the covering unitwhich are substantially rigidly connected with open front ends ofspacers, via plastic welding connections in particular. Such weldingconnections may be realised in that the thermoplastic is heated by meansof heat rays, for instance, but also via RF or ultrasonic welding. Thecovering layer closes the individual resonance chambers both outwardlyand between each other.

The covering layer for instance consists of a thin layer ofthermoplastics like polypropylene, for instance. However, it may alsoconsist of a fleece. It is preferably configured as a composite materiallike a laminate of different individual layers. The layer thicknessshould be situated in the range between 0.5 and 8 mm.

It may be useful for some applicational cases to produce the coveringlayer from a double layer which on the one hand consists of a thin metallayer of aluminium, in particular, having a thickness between 5 and 200μm and on the other hand of a thermoplastic plastic like polypropylene,for instance, and/or a fleece which is attached to the side of thealuminium layer facing the basic constructional unit. This thermoplasticlayer than constitutes the connecting layer towards the edge of thesupporting body on the one hand and towards the front ends of thespacers on the other hand.

The two constructional units are preferably produced via the followingprocess:

First a flat blank or a flat web of the single-layered or multi-layeredcovering layer is tentered in a straight plane over the preformed basicconstructional unit. Subsequently, a stamp is pressed onto the coveringlayer in the direction towards the basic constructional unit. The stampfront face comprises sort of a “countersurface” against the surfacewhich the covering unit is to occupy in the final state of the basicconstructional unit. Thus, the stamp serves as a deformation tool sinceit deforms the covering layer and presses it onto the open front ends ofthe spacers and the edge of the basic constructional unit. Due to thisdeformation, the covering layer assumes the moulded shape wherein itconstitutes the covering unit for the absorber. Said layer issimultaneously attached to the basic constructional unit so that it doesnot “spring back” into its flat initial state.

During this deformation process, the thin covering layer is set ontothat side of the basic constructional unit which comprises the openfront edges of the spacers between which the intermediate cavities aresituated.

Attachment of the covering unit, i.e. connection of the adjacentportions, namely of the edge of the supporting body and open front endsof the desired spacers with the supporting body is more particularlyeffected via the use of pressure and heat in the case thermoplasticmaterials or thermoadhesives. The covering unit may as well be providedwith a self-adhering adhesive layer on that side which faces the basicconstructional unit, namely the edge and the open front ends of thespacers.

The process feature reading that the deformation of the covering layerand the rigid connection thereof with the preformed basic constructionalunit should be effected in the very same tool immediately subsequentlyin time, which is above all helpful in reducing the production time anddecreasing the loss of heat energy.

The advantage of the rigid connection also resides in that acharacteristic, which might possibly be inherent to the covering layer,namely a more or less rapid, renewed deformation from the preformedconfiguration into the initially flat configuration in the course oftime, is counteracted. In this respect, there exist more possibilites touse different materials. However, it is essential that the covering unitmay vibrate freely, at least in regions between the front ends or,respectively, the front edges of the spacers, and that sound waves aretransferred into the intermediate cavities so that sound energy may bedampened or, respectively, absorbed within the chamber-like intermediatecavities between the basic constructional unit on the one hand and thecovering unit on the other hand.

Instead or in addition thereto, the covering unit may also be providedwith holes enabling sound waves to pass through.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, a preferred embodiment of the invention will bedescribed in detail upon reference to the drawing; therein:

FIGS. 1 to 3 show method steps for the production of an absorberaccording to the invention in a schematic representation;

FIG. 4 shows a part-section of an absorber according to the invention;and

FIGS. 5 to 8 show method steps of a variant method.

DETAILED DESCRIPTION OF THE INVENTION

According to FIG. 1, a basic constructional unit 10 is set onto a base12. Basic constructional unit 10 consists of a supporting body 1wherefrom spacers 2 having differing lengths protrude towards the sidefacing away from base 12. Spacers 2 and supporting body 1 consist of thesame material, i.e. polypropylene in this example, and are preformed viatransfer moulding. Upwards of edge 4 of basic constructional unit 10, athin covering layer 5 made of polypropylene is tightly tentered in astraight plane. Upwards therefrom, there is provided a stamp 8 having afront face 9 which is substantially formed according to theconfiguration the covering layer 5 is to assume after deformationthereof and connection with the basic constructional unit 10.

Now, stamp 8 is pressed downwards in the direction indicated by thearrows, from the position shown in FIG. 1 into the position shown inFIG. 2 in the direction of base 12, covering layer 5 being deformed suchthat it nestles against the outer contours of front face 9 and therebycontacts edge 4 of supporting body 1 as well as open front ends 3 ofspacers 2 too. Via the use of pressure and heat in particular, it isprovided for that strong and rigid connections are produced betweencovering unit 11, i.e. presently deformed covering layer 5, and basicconstructional unit 10 at these “contact locations”.

In a further method step according to FIG. 3, stamp 8 is again liftedoff the now finished absorber in the direction indicated by the arrows,chamber-like intermediate cavities 7 being created between basicconstructional unit 10, i.e. in supporting body 1 and web-shaped spacers2 on the one hand and covering unit 11.

The invention substantially facilitates production since the coveringunit need not be preformed. It is recommended to simultaneously deformand weld covering layer 5 with basic constructional unit 10 or,respectively, connect them in any other manner. For the purpose,covering layer 5 may also comprise an adhesive layer on that side wherejunctions 6 are to be created. Covering layer 5 may also be configuredto be multi-layered. Thus, the outer layer may consist of an aluminiumfoil and the side facing the basic constructional unit may consist of athermoplastic layer which melts during heating and connects to openfront ends 3 or, respectively, edge 4 of basic constructional unit 10,in case thermoplastic material is used there too.

Inductive heating methods may also be used if aluminium is employed sothat stamp 8 itself need not necessarily be heated to the softeningtemperature although this has proven to be advantageous in many cases.

According to FIG. 4, covering unit 11 consists of a polypropylene layerhaving a thickness of 1 mm, which is connected with basic constructionalunit 10 by means of plastic weld connections along the open front ends 3of spacers 2, i.e. at the rigid functions 6. However, covering unit 11is able to vibrate in the regions between rigid junctions 6, as isindicated by the arrows. Therefore the vibrant portions of covering unit11 are defined by the thickness and the material of covering layer 5 onthe one hand and by the spacing of rigid junctions 6 on the other hand.Incident air sound is transferred to the gas space in the chamber-likeintermediate cavities 7 via vibrating covering layer 5, optionally in anattenuated form. According to the dimensioning of intermediate cavities7 as well as to the material of the walls thereof, specific frequencyranges may be dampened selectively. Basic constructional unit 10 iscoated with a protective layer la on the underside.

FIGS. 5 to 8 show a different method variant for producing the absorberaccording to the invention in schematic sectional views. First, thepreformed basic structural unit 10, which is set onto base 12, is heatedwith the aid of a heating tool 18 on the side facing away from the base12, i.e. the facing-away surfaces of surrounding edge 4 as well as atopen free ends 3 of spacers 2. Heating is carried out to such an extentthat the surfaces of open front ends 3 and of edge 4 of basicconstructional unit 10, which face heating tool 18, melt open.

Then, heating tool 18, which effects, according to FIG. 5, plasticizingof the plastic material of basic constructional unit 10 via radiationheat or also by direct contact on the respective surfaces, is lifted offand a covering layer 5, which may also consist of several part-layers,is tentered at a spacing from basic constructional unit 10 in the mannerindicated in FIG. 6.

Subsequently, a press stamp 8 is set onto covering layer 5 from above insuch a manner according to FIG. 7 that said layer deforms incorrespondence with the configuration of the respective front face ofstamp 8 and is pressed onto the molten-open portions of edge 4 and openfront ends 3 of basic constructional unit 10 in the deformation statewhich is schematically shown in FIG. 7. Pressing is carried out untilthe plasticised material has been sufficiently solidified again so thata rigid mechanical connection is produced at the junctions 6 between thepreviously molten-open surfaces of edge 4 and open front ends 3 ofspacers 2 on the one hand and the respective counter-surfaces of thincovering layer 5 on the other hand. Now stamp 8 may be removed so thatthere results the finished absorber which is shown in cross-section inFIG. 8 to have chamber-like intermediate cavities 7 between basicconstructional unit 10 and preformed covering unit 11. As it were, allchambers 7 are completely closed while those portions of covering unit11, which are situated between junctions 6 between basic constructionalunit 10 and covering unit 11, still are able to vibrate.

In this alternative production method, it is also recommended to usethermoplastics for covering layer 5. It is more particularly recommendedto use polypropylene. For certain applicational cases, a foamed layer ofpolypropylene is preferably used which has a layer thickness of about0.5 to 10 mm. This thin foamed layer acts, as it were, as a “membrane”in those regions which cover chamber-like intermediate cavities 7. Whenthe deformed thin covering layer 5 of PP foam is pressed on according toFIG. 7, for instance, the respective contact locations melt open untilthey are sufficiently plasticised in order to form a mechanically rigidconnection with basic constructional unit 10 after cooling.

According to a further configuration of the invention, covering layer 5comprises a fleece layer on the side facing basic constructional unit 10unless it is even the whole covering layer 5 which consists of fleecefabric. PP fibers are preferably used for the fleece fabric so thatthere also occur melt or, respectively, melt-open processes. However, ithas turned out that a sufficiently rigid mechanical connection withbasic constructional unit 10 is possible, using the method according toFIGS. 5 to 10, if fleece fabrics made of fiber material, even withoutmelting or melting-open thereof, since the protruding fiber particlesbecome embedded in plasticised plastic to such an extent that there arecreated enough “anchorage locations” in the regions of junctions 6 afterthe plastic has cooled down and solidified. As at it were, the fibers“dig themselves in” if covering layer 5 is pressed sufficiently stronglyonto basic constructional unit 10 or, respectively, its edge 4 and theopen front ends 3 of spacers 2.

What is claimed is:
 1. An absorber for absorbing acoustic sound waves,comprising a basic constructional unit (10) including a supporting body(1) and spacers (2) which protrude from the supporting body, and acovering unit (11) comprising a covering layer (5) connected to thespacers (2) of the supporting body (1) to close chamber-likeintermediate cavities (7) between the supporting body (1) and spacers(2), wherein the spacers (2) are integrally preformed with thesupporting body (1), the covering layer (5) being deformed, thin andable to vibrate in certain regions at least, said covering unit (11)being substantially rigidly connected both with an edge (4) of the basicconstructional unit (10) and with open front ends (3) of spacers (2)characterized in that the basic constructional unit (10) consists ofdeep-drawn, transfer-moulded or injection-moulded thermoplastic orthermosetting material.
 2. An absorber according to claim 1,characterized in that the basic constructional unit (10) is offiber-reinforced plastic.
 3. An absorber according to claim 1 or 2,characterized in that the covering unit (11) is deformed and solidifiedin a deformed shape.
 4. An absorber according to claim 1, characterizedin that the covering unit (11) is connected to the open front ends (3)of spacers (2) by rigid connections (6) defined by plastic weldingconnections.
 5. An absorber according to claim 1, characterized in thatthe covering unit (11) comprises at least two layers, the covering layerfacing the basic constructional unit (10) and comprising thermoplasticmaterial.
 6. An absorber according to claim 5, characterized in that thethermoplastic material of the covering layer (5) of the covering unit(11) comprises polypropylene, the covering unit (11) being thin.
 7. Anabsorber according to claim 1, characterized in that the covering layer(11) is thin and comprises a thin aluminum layer.
 8. A method forproducing an absorber for absorbing acoustic sound waves, comprising asupporting body (1) and spacers (2) which protrude from the supportingbody, and a covering layer (5) connected to the spacers (2) of thesupporting body (1) to close chamber-like intermediate cavities (7)between the supporting body (1) and spacers (2), wherein the spacers (2)are integrally preformed with the supporting body (1) to define a basicconstructional unit (10), the covering layer (5) being included in acovering unit (11) applied onto the basic constructional unit (10), thecovering unit (11) being deformed and thin, the covering unit (11) beingable to vibrate in certain regions at least, wherein the covering layeris deformed and connected with the basic constructional unit,characterized in that the method comprises the steps of: performing thebasic constructional unit (10); subsequently deforming the covering unit(11) from a more particularly straight plane, directly onto open frontends (3) of the spacers (2) and onto an edge (4) of the preformed basicconstructional unit (10) by means of a stamp (8) which is configured tohave a front face (9) in correspondence with the contours of thefinished covering unit (11); and connecting, using pressure and/or heat,the covering unit (11) to the basic constructional unit (10).
 9. Amethod according to claim 8, characterized in that the step of deformingthe covering unit (11) by the stamp (8) comprises heating the coveringunit (11) at least until the plastic at junctions of the covering unit(11) with the basic constructional unit (10) have softened.
 10. A methodaccording to claim 8 or 9, characterized in that the step of connectingthe covering unit (11) to the basic constructional unit (10) comprisesproviding in a molten open condition, the open front ends (3) of spacers(2) and the edge (4) of the preformed basic constructional unit (10)and, subsequently, dressing the covering unit (11) onto the plasticisedfront ends (3) by means of the configured stamp (8), and cooling tosolidify the front ends (3) to mechanically connect the front ends tothe covering unit (11).
 11. A method according to claim 8, characterizedin that the step of connecting the covering unit (11) to the basicconstructional unit (10) comprises heating, via inductive heating of analuminum layer forming part of the covering unit (11), the plastic ofthe covering layer (5) at the functions with the basic constructionalunit (10).
 12. An absorber for absorbing acoustic sound waves,comprising: a basic constructional unit (10) including a supporting body(1), and integrally preformed spacers (2) protruding from saidsupporting body (1), the basic constructional unit (10) being ofdeep-drawn, transfer-molded or injection molded thermoplastic orthermosetting material; and a covering unit (11) comprising a coveringlayer (5) being connected with the basic constructional unit (10) andclosing chamber-like intermediate cavities (7) between the supportingbody (1), spacers (2) and covering layer (5) wherein said covering layer(5) is deformed and thin, said covering layer (5) having at least someregions able to vibrate in a membrane-like manner to transfer soundwaves into said intermediate cavities (7) and wherein said covering unit(11) is substantially rigidly connected with an edge (4) of the basicconstructional unit (10) and with open front ends (3) of the spacers (2)by rigid connections (6).
 13. An absorber according to claim 12,characterized in that the basic constructional unit (10) isfiber-reinforced plastic.
 14. An absorber according to claim 12 or 13,characterized in that said covering unit (11) is thin, said coveringunit being deformable to a deformed shape and able to be solidified inthe deformed shape.
 15. An absorber according to claim 12, characterizedin that the covering unit (11) is connected to the open front ends (3)of spacers (2) by rigid connections (6) defined by plastic weldingconnections.
 16. An absorber according to claim 12, characterized inthat the covering unit (11) comprises at least two layers, the coveringlayer facing the basic constructional unit (10) and comprisingthermoplastic material.
 17. An absorber according to claim 16,characterized in that said thermoplastic material of the covering layer(5) of the covering ring unit (11) comprises polypropylene, the coveringunit (11) being thin.
 18. An absorber according to claim 12,characterized in that said covering unit (11) is thin and comprises athin aluminum layer.
 19. A method for producing an absorber forabsorbing acoustic sound waves, the method comprising the steps of:deep-drawing, transfer-molding or injection molding thermoplastic orthermosetting material to form a basic constructional unit (10);performing the basic constructional unit (10) to have spacers (2)protruding from an integral supporting body (1); deforming a coveringunit (11) comprising a covering layer (5) from a more particularlystraight plane, directly onto open front ends (3) of said spacers (2)and onto an edge (4) of the preformed basic constructional unit (10) bymeans of a stamp (8) which is configured to have a front face (9) incorrespondence with the contours of the finished deformed covering unit(11); and connecting the covering layer (5), using pressure and/or heat,to the basic constructional unit (10) to close chamber-like intermediatecavities (7) between the supporting body (1) and spacers (2), saidconnection of the covering layer (5) both with the edge (4) of the basicconstructional unit (10) and with open front ends (3) of the spacers (2)being by a substantially rigid connection (6) such that the coveringlayer (5) is deformed and thin, and such that the covering layer (5) isable to vibrate at least in certain regions in a membrane-like mannerthereby transferring sound waves into said intermediate cavities (7).20. A method according to claim 19, characterized in that the step ofdeforming the covering unit (11) by the stamp (8) comprises heating thecovering unit (11) at least until the plastic at junctions of thecovering unit (11) with the basic constructional unit (10) havesoftened.
 21. A method according to claim 19 or 20, characterized inthat the step of connecting the covering unit (11) to the basicconstructional unit (10) comprises heating the open front ends (3) ofspacers (2) and the edge (4) of the preformed basic constructional unit(10) and subsequently, pressing the covering unit (11) onto theplasticised front ends (3) by means of the configured stamp (8), andcooling the front ends (3) thereby to solidify the front ends such thatthe front ends are mechanically connected to the covering unit (11). 22.A method according to claim 19, characterized in that the step ofconnecting the covering unit (11) to the basic constructional unit (10)comprises heating, via inductive heating of an aluminum layer formingpart of the covering unit (11), the plastic of the covering layer (5) atthe junctions with the basic constructional unit (10).
 23. An absorberfor acoustic waves, comprising: a supporting body; spacers protrudingfrom said supporting body to define chamber-like intermediate cavitiesbetween said supporting body and spacers; and a covering layer connectedto said spacers to close said intermediate cavities, said covering layerhaving resilient portions between said spacers to vibrate to transferacoustic waves into said intermediate cavities.
 24. An absorberaccording to claim 23, wherein said intermediate cavities are sized toprovide selective dampening of specific acoustic frequency ranges. 25.An absorber according to claim 23, wherein said intermediate cavitiesare defined by inner surfaces of said supporting body, spacers andcovering layer of a material for providing selective dampening ofspecific acoustic frequency ranges.
 26. An absorber according to claim23, wherein said spacers each have a front end, said spacers each havinga respective length defined by the dimension between said supportingbody and said respective front end, said respective lengths of saidspacers being different.
 27. An absorber according to claim 23, whereinsaid covering layer is connected to said spacers and supporting body byrigid connections.
 28. An absorber according to claim 23, wherein saidspacers are integrally connected to said supporting body.
 29. Anabsorber according to claim 23, wherein said spacers and supporting bodyare of thermoplastic or thermosetting material.
 30. An absorberaccording to claim 23, wherein said spacers and supporting body are ofpolypropylene.
 31. An absorber according to claim 23, wherein theportions of said covering layer and spacers directly contacting oneanother, and the portions of said covering layer and supporting bodydirectly contacting one another are formed of fiber-reinforced plastic.32. An absorber according to claim 23, wherein said covering layer is ofthermoplastic material.
 33. An absorber according to claim 23, whereinsaid covering layer is of polypropylene.
 34. An absorber according toclaim 33, wherein said covering layer is of foamed polypropylene havinga thickness of between 0.5 and 10 mm.
 35. An absorber according to claim23, and further comprising an aluminum layer connected to said coveringlayer.
 36. An absorber according to claim 35, wherein said aluminumlayer contacts the side of said covering layer facing away from saidspacers.
 37. An absorber according to claim 35, and further comprising apower source connected to said aluminum layer for heating said aluminumlayer.
 38. An absorber according to claim 37, wherein said power sourceprovides electrical power to said aluminum layer.
 39. An absorberaccording to claim 23, and further comprising an adhesive materialbetween the portions of said covering layer directly contacting saidsupporting body, and between the portions of said covering layerdirectly contacting said spacers to provide said connectionstherebetween.
 40. An absorber according to claim 23, and furthercomprising a protective layer connected to the surface of saidsupporting body facing away from said spacers.
 41. A method for makingan absorber for acoustic waves, the method comprising the steps of:forming a supporting body; forming spacers connected to the supportingbody to define chamber-like intermediate cavities between the supportingbody and spacers; deforming a covering layer directly onto the spacersand onto the supporting body by a stamp having a front facecorresponding to the contours of the spacers and supporting body, thefront face of the stamp being continuous so that said deforming of thecovering layer onto the spacers and supporting body closes theintermediate cavities; and connecting the deformed covering layer to thespacers and supporting body such that resilient portions of the coveringlayer between the spacers and supporting body vibrate to transfer soundwaves into the intermediate cavities.
 42. A method according to claim41, wherein said forming steps comprise forming said supporting bodyintegrally with said spacers.
 43. A method according to claim 41,wherein a portion of the front face of the stamp is planar between apair of adjacent spacers, said deforming step deforming the portion ofthe covering layer adjoining the portion of the front face into acontour defined by a planar surface containing the pair of adjacentspacers.
 44. A method according to claim 41, wherein a portion of thefront face of the stamp is recessed relative to a pair of adjacentspacers, said deforming step deforming the portion of the covering layeradjoining the portion of the front face into a contour defined by anon-planar surface containing the pair of adjacent spacers.
 45. A methodaccording to claim 41, wherein said steps comprise the steps ofdeep-drawing, transfer-moulding or injection molding thermoplastic orthermosetting material to form the supporting body and spacers.
 46. Amethod according to claim 41, wherein said connecting step comprises thestep of forcibly pressing the covering layer against the supporting bodyand spacers.
 47. A method according to claim 41 and further comprisingthe step of heating to soften the covering layer and/or the supportingbody and spacers before or contemporaneously with said deforming step,wherein said connecting step comprises solidifying the covering layerand/or spacers and supporting body to provide the connectiontherebetween.
 48. A method according to claim 47, wherein said heatingstep comprises heating the stamp before and/or contemporaneously withsaid deforming step.
 49. A method according to claim 47, and furthercomprising the step of connecting an aluminum layer to the coveringlayer, said heating step comprising heating the aluminum layer.
 50. Amethod according to claim 49, wherein said heating step compriseselectrically heating the aluminum layer.
 51. A method according to claim41, and further comprising the steps of: forming the covering layer ofthermoplastic; and connecting an aluminum layer to the side of thecovering layer facing away from the spacers, said step of connecting thealuminum layer preceding said step of connecting the deformed coveringlayer to the spacers and supporting body, said step of connecting thedeformed covering layer comprising heating the covering layer to amelted condition, positioning the melted covering layer into directcontact with the spacers and supporting body, and solidifying the meltedcovering layer to provide the connection between the covering layer, andthe spacers and supporting body.
 52. A method according to claim 41,wherein said connecting step comprises the step of forming rigidconnections between the covering layer, and the spacers and supportingbody.
 53. A method according to claim 41, wherein the covering layer,supporting body and spacers are of plastic material, and furthercomprising the step of positioning fibrous material between the portionsof the covering layer and spacers directly contacting one another, andbetween the portions of the covering layer and supporting body directlycontacting one another before said deforming step, said deforming stepcomprising applying pressure and/or heat to the covering layer,supporting body and spacers to anchor the fibrous material in thecovering layer, supporting body and spacers to provide afiber-reinforced connection of the covering layer to the spacers andsupporting body.
 54. A method according to claim 41, and furthercomprising the step of forming the covering layer to have a planarcontour, said step of forming the covering layer being before saiddeforming step.